CN115295802A - Adhesive, preparation method thereof and application thereof in lithium ion battery - Google Patents

Abstract

The invention provides an adhesive, a preparation method thereof and application thereof in a lithium ion battery. The adhesive comprises a polymer with a side chain containing functional groups, inorganic particles and a solvent; the mass ratio of the polymer containing functional groups on the side chains to the inorganic particles is 10: 2-2: 10; the inorganic particles include conductive inorganic particles and ion conductive inorganic particles; the mass ratio of the conductive inorganic particles to the ion-conductive inorganic particles is 10:1 to 1:10. the invention has the advantages that: the problem of volume expansion of the silicon-based negative electrode is inhibited by utilizing the thermal crosslinking effect among the adhesive components, and the cycling stability of the silicon and tin negative electrodes is improved; and secondly, the ion conducting component of the adhesive has the function of transmitting ions, which is beneficial to improving the rate capability of the lithium battery.

Description

A kind of adhesive and preparation method thereof and application in lithium ion battery

technical field

The application relates to an adhesive, its preparation method and its application in lithium-ion batteries, belonging to the technical field of new polymer materials.

Background technique

Lithium-ion batteries have excellent properties such as high working voltage, high specific energy, and long cycle life, and have been widely used in mobile devices, electric vehicles, aerospace and other fields. Lithium-ion batteries are mainly composed of current collectors, active materials, adhesives, conductive agents, separators, etc. The nature of the active material determines the type and properties of the adhesive used. At present, most lithium battery manufacturing processes use polyvinylidene fluoride (PVDF) as the adhesive between the positive electrode material and the current collector, while the bonding between the negative electrode material and the current collector mainly uses styrene-butadiene rubber emulsion/carboxymethyl cellulose Complex (SBR/CMC).

The positive electrode binder is mainly PVDF, and PVDF has an inherent reaction, that is, it will form a defluorination reaction with hydrogen under strong alkalinity, which will cause PVDF jelly gel during the positive electrode mixing process. Therefore, the electrode material mixing process needs to strictly control the environmental humidity. Moreover, fluorine pollution and fluorine recovery are major problems that must be faced in the subsequent battery material recycling process.

SBR/CMC and acrylonitrile-acrylate copolymer adhesives are often used for bonding graphite anode materials. That is because the volume change of the graphite negative electrode is small during the charge and discharge process, and the bonding strength of SBR and acrylate is sufficient to prevent the graphite powder from falling off or from the current collector. However, for anode materials such as silicon and tin with high specific capacity, due to the huge volume change in the charging and discharging process, it is difficult for the commonly used SBR and acrylate adhesives to control the pulverization of silicon and tin electrode materials, which eventually leads to cycle failure. Performance plummeted.

The reason why PVDF and acrylonitrile-acrylate copolymers are the preferred binders for ion battery electrode materials is mainly because the C-F bond and -CN bond in the polymer structure have good ion transport and electrochemical stability. Although most commonly used polymers have strong adhesive properties, their low ionic conductivity limits their application in the bonding of lithium-ion battery materials.

The study found that the Lewis acid center on the surface of the nanoparticles can interact with the anion of the lithium salt, thus weakening the interaction between the polar atoms in the polymer and Li ⁺ , promoting the dissociation of the lithium salt, and then releasing free Li ⁺ to improve the lithium ion concentration. ion conduction efficiency. Therefore, nanoparticles are mainly used to prepare composite polymer electrolytes for lithium-ion batteries. There are also a small number of studies on the use of nanoparticles for the manufacture of lithium-ion battery adhesives, but all of them require the addition of coupling components to assist crosslinking. Samsung SDI Co., Ltd. (Chinese patent CN 103242595 B) reported that a composition composed of inorganic particles, binder prepolymer and organic-inorganic coupling agent was used to bond silicon and tin negative electrodes. The silicon and tin negative electrodes are anchored on the inorganic particles and the adhesive through the coupling agent, which can well inhibit the volume expansion of the silicon and tin negative electrodes.

Contents of the invention

In view of the above-mentioned problems of volume expansion of the negative electrode and low ion conductivity of commonly used polymers, the present invention provides an adhesive composition that can be applied to the positive and negative electrodes of lithium-ion batteries. The adhesive composition can effectively limit the volume expansion of the tin negative electrode through simple heat treatment without adding a coupling agent; secondly, the adhesive composition uses the ion transport function of nanoparticles to make up for the low ion conductivity of conventional polymers. , broaden the selection range of adhesive polymers, and provide a technical solution for lithium-ion battery adhesives without fluorination; furthermore, the adhesive composition is helpful for the transmission of lithium ions, which can effectively improve the rate performance of lithium-ion batteries.

According to one aspect of the present application, an adhesive is provided, the adhesive includes a polymer, conductive inorganic particles and ion-conducting inorganic particles;

The polymer is obtained by polymerization of monomers containing functional groups on the side chain;

The functional group is selected from at least one of hydroxyl group, carboxyl group, amino group, isocyanate group, epoxy group or ester group;

Optionally, the polymer is selected from polyurethane, polyvinyl alcohol, polyacrylic acid, polyvinyl acetate, polyacrylamide, carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose At least one of cellulose or hydroxyethyl cellulose;

In the present application, inorganic particles, unless otherwise specified, are a general term for conductive inorganic particles and ion-conducting inorganic particles. The study found that alkali metal ions or alkaline earth metal ions are considered to be able to diffuse along the interface region of nanoparticles, that is, some nanoparticles may have the transport function of lithium ions or sodium ions, which can improve ion conduction efficiency. There are different conclusions about the transport and conduction mechanism of lithium ions at the nanoparticle interface, one of which is the Lewis acid-base theory: the Lewis acid center on the surface of the nanoparticle can interact with the anion of the lithium salt, thus weakening the polarity in the polymer The interaction between atoms and Li ⁺ promotes the dissociation of lithium salt, and then releases free Li ⁺ to improve the ion conduction efficiency of lithium ions. And the higher the specific surface area of the nanoparticles, the better the ion conductivity. In this specification, these particles with the lithium ion transport function are collectively referred to as "ion-conducting inorganic particles".

The ratio of the mass of the polymer to the sum of the masses of the conductive inorganic particles and the ion-conducting inorganic particles is 10:2 to 2:10;

Preferably, the ratio of the mass of the polymer to the sum of the masses of the conductive inorganic particles and the ion-conducting inorganic particles is 10:3-3:10;

The mass ratio of the conductive inorganic particles to the ion-conducting inorganic particles is 10:1˜1:10.

The conductive inorganic particles are selected from at least one of metal particles, graphite, acetylene black or carbon nanotubes;

The metal particles are selected from at least one of Be, Al, Ti, V, Fe, Co, Zn, Ge, Zr, Ag, Sn, Au or Mn;

The ion-conducting inorganic particles are selected from at least one of metal oxides, non-metal oxides or metal fluorides;

The metal oxide is selected from at least one of oxides of Be, Al, Ti, V, Fe, Co, Zn, Ge, Zr, Ag, Sn, Au or Mn;

The non-metallic oxide is selected from silicon dioxide;

The metal fluoride is at least one selected from the fluorides of Be, Al, Ti, V, Fe, Co, Zn, Ge, Zr, Ag, Sn, Au or Mn.

According to another aspect of the present application, a kind of preparation method of above-mentioned adhesive is provided, at least comprises the following steps:

The adhesive is obtained by mixing raw materials containing polymers, conductive inorganic particles, ion-conductive inorganic particles and solvents.

Described mixing comprises the following steps:

Dissolving the conductive inorganic particles and the ion-conducting inorganic particles in a solvent to obtain a mixture I;

Dissolving the polymer in a solvent yields mixture II;

mix mixture I and mixture II;

The mixing temperature is 25-100°C.

The solvent is selected from at least one of water, N-methylpyrrolidone, dimethylformamide, tetrahydrofuran, acetone, butanone, ethanol, isopropanol or acetonitrile;

The mass of the solvent: the sum of the masses of the polymer, conductive inorganic particles and ion-conducting inorganic particles = 20:1 to 1:1;

Optionally, the raw material also contains a wetting agent;

The wetting agent is selected from alkyl sulfates, sulfonates, fatty acids, fatty acid ester sulfates, carboxylic acid soaps, phosphoric acid esters, polyoxyethylene alkylphenol ethers, polyoxyethylene fatty alcohol ethers, polyoxyethylene At least one of polyoxypropylene block copolymer or silanol nonionic surfactant;

The content of the wetting agent is 0-5.0wt% of the adhesive;

Optionally, the raw material also contains a thickener;

The thickener is selected from low-molecular thickeners and/or high-molecular thickeners;

The low molecular weight thickener is selected from inorganic salt thickeners, fatty alcohols, fatty acid thickeners, alkanolamide thickeners, ether thickeners, ester thickeners or amine oxide thickeners at least one of;

The polymer thickener is selected from at least one of cellulose thickeners, polyacrylic thickeners, polyurethane thickeners, natural rubber thickeners or polyoxyethylene thickeners.

The content of the thickener is 0-5.0wt% of the adhesive.

According to another aspect of the present application, a positive electrode material for a lithium ion battery is provided, the positive electrode material contains the above adhesive or the adhesive obtained by the above preparation method.

According to another aspect of the present application, a negative electrode material for a lithium ion battery is provided, the negative electrode material contains the above adhesive or the adhesive obtained by the above preparation method.

According to another aspect of the present application, a lithium-ion battery is provided, the positive electrode of the lithium-ion battery adopts the above-mentioned positive electrode material;

or/and;

The negative electrode of the lithium ion battery adopts the above-mentioned negative electrode material.

The adhesive provided by the invention can effectively neutralize the alkaline substances produced by the interaction between the positive electrode material and water, and at the same time, the adhesive provided by the invention is also suitable for silicon and tin negative electrodes.

In order to achieve the above object, the adhesive of the present invention mainly includes: polymers containing functional groups on the side chains (i.e. "polymers in the claims"), conductive inorganic particles (i.e. "conductive inorganic particles in the claims") ), ion-conducting inorganic particles (that is, "ion-conducting inorganic particles in the claims"). The ion-conducting particles have the function of conducting ions at the interface, and the conductive inorganic particles have the function of conducting electrons. When the content of inorganic particles in the adhesive can form a conductive network and an ion interface transport network, the ion and electron transport efficiency of the electrode can be improved to the greatest extent, thereby improving the rate performance of the lithium-ion battery.

When used as an adhesive for silicon and tin negative electrodes, the hydroxyl groups on the surface of the ion-conducting inorganic particles react with the functional groups on the polymer side chains to form a cross-linked structure at high temperature, thereby controlling the volume change of the silicon and tin negative electrodes.

When the adhesive is used, heat crosslinking treatment is required, and the heat crosslinking temperature is 80-200°C, preferably, the heat crosslinking temperature is 100°C-150°C. The purpose is that when the adhesive is used for bonding electrode materials of lithium-ion batteries, the polymer containing functional groups on the side chains in the adhesive undergoes a cross-linking reaction with the ion-conducting inorganic particles.

In the adhesive, the conductive inorganic particles have a particle diameter of 1 nm to 2000 nm, and optionally, the particle diameter is 1 nm to 200 nm.

In the adhesive, the particle size of the ion-conducting inorganic particles is 10 nm-20 μm, and optionally, the particle size is 10 nm-2 μm.

The viscosity of the adhesive at 25° C. is ≥1000 mPa·s, and the inorganic particles are not easy to settle.

The concrete preparation process of described adhesive is as follows:

A. Wetting of inorganic particles (including: conductive inorganic particles, ion-conducting inorganic particles)

Immerse conductive inorganic particles and ion-conducting inorganic particles in a certain amount of solvent, stir for 30 minutes and then let it stand for 24 hours. If necessary, add a wetting agent;

B. Dissolution of polymers containing functional groups on the side chain

Use the solvent in A to dissolve the polymer. If there is heating to promote dissolution, it needs to be cooled before proceeding to the next step.

C, preparation of polymer/inorganic particle adhesive containing functional groups on the side chain

The dissolved polymer and the wet particles are dispersed at a high speed, and a thixotropic agent is optionally added to adjust the viscosity to obtain the adhesive.

Described adhesive can be applied to the preparation of the electrode of lithium-ion battery and button battery thereof, and its preparation method is as follows:

1) Preparation of electrode slurry: mix electrode material, adhesive and conductive agent, and ball mill for 2 hours;

2) Coating: evenly coat the electrode slurry on the aluminum foil (copper foil), and dry it under vacuum at 80-200°C for 12 hours;

3) Die-cutting of the pole piece: After the vacuum-dried pole piece is rolled, it is punched to obtain a circular electrode piece with a diameter of 16mm;

4) Preparation of button-type half-cells: After the circular electrode sheet was vacuum-dried at 80°C for 12 hours, it was transferred to a dry argon glove box and paired with metal lithium to form a button-type half-cell. The electrolyte was 1mol/L lithium hexafluorophosphate (solvent: Ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1 (V)); Add 3wt% functional additive tris(trimethylsilyl) in electrolyte ) phosphate or fluoroethylene carbonate (FEC); the diaphragm is a polypropylene diaphragm.

The electrode material can be positive electrode material or negative electrode material. The positive electrode material includes positive electrode materials such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide and manganese nickel cobalt composite oxide. Specific examples of such positive electrode materials include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ and LiMn ₂ O ₄ , LiMn _x Ni _y Co _1-xy O ₂ , LiVO ₂ , Li _x V ₂ O ₄ , Li _x V ₃ O ₈ , LiFeO ₂ , LiFePO ₄ . Wherein, the range of x is 0.1-2; the range of y is 0.1-2;

The negative electrode material can be artificial graphite, natural graphite, activated carbon, silicon-based negative electrode material, tin-based negative electrode material.

In the coating operation during the preparation process of the lithium-ion battery electrode, it is known that aluminum foil is used as a current collector for the positive electrode, and copper foil is used as the current collector for the negative electrode.

In the coating operation during the preparation process of the lithium-ion battery electrode, the electrode needs to be vacuum-heated at 80-200°C. The reason why the electrodes need to be heat-treated at 80-200° C. is to promote the thermal cross-linking reaction between the polymer of the functional group on the side chain in the composition and the inorganic particles.

The conductive agent is selected from conductive carbon black, carbon nanotubes or graphene;

The dosage ratio of the electrode material to the conductive agent is 65:35 to 99:1;

Preferably, the time of the ball milling is 1h to 5h;

Preferably, the drying temperature is 80-200°C;

Preferably, the drying time is 4 to 24 hours;

Preferably, the drying is carried out under vacuum conditions;

Preferably, the drying vacuum is -0.02˜-0.1 MPa.

The benefit of the present invention is that the thermal crosslinking effect between the adhesive components is used to suppress the volume expansion of silicon-based negative electrodes, and improve the cycle stability of silicon and tin negative electrodes; furthermore, the ion transport function of nanoparticles is used to compensate The problem of low ion conductivity of conventional polymers provides a feasible technical solution for the non-fluorination of lithium ion adhesives.

Description of drawings

Figure 1: Adhesive D-differential scanning calorimetry (DSC) spectrum.

Figure 2: The cycle rate curve of the lithium-ion battery prepared by applying the adhesive to the positive electrode material (NMC622).

Figure 3: The cycle rate curve of the lithium-ion battery prepared by applying the adhesive to the positive electrode material (LFP).

Figure 4: The cycle curve of the prepared lithium-ion battery when the adhesive is applied to the negative electrode material (S600).

Detailed ways

The present application is described in detail below in conjunction with the examples, but the present application is not limited to these examples. The raw materials and reagents in the examples of the present application were purchased through commercial channels.

Nano silicon oxide: hydrophilic, specific surface area 420m ² /g, Shanghai McLean Biochemical Technology Co., Ltd.

Nano-alumina: hydrophilic, particle size 30nm, Shanghai McLean Biochemical Technology Co., Ltd.

Conductive carbon black: Super-P conductive agent, Shenzhen Vidifi New Energy Technology Co., Ltd.

Polyvinyl alcohol, alcoholysis degree 80-99%, Shanghai McLean Biochemical Technology Co., Ltd.

NMC622: LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , Hunan Shanshan New Material Co., Ltd.

LFP: lithium iron phosphate, Hunan Shanshan New Material Co., Ltd.

Silicon carbon anode: S600, Shenzhen Betterray New Energy Materials Co., Ltd.

The analytical method in the embodiment of the application is as follows:

The thermal crosslinking temperature of the adhesive was tested by differential scanning calorimetry (TA Instruments DSC Q200).

Battery Electrochemical Performance

The first measurement of charging specific capacity, charging capacity and discharging capacity was carried out by using the LanDian battery test system (model: LAND-CT2001A, purchased from Wuhan LanDian Electronics Co., Ltd.).

Evaluation of cycle and rate performance of coin half cells:

At 25°C, put the assembled button-type half-cell at rest for 8 hours, first charge it at a rate of 0.1C to 4.2V), let it stand for 3 minutes, then discharge it at a rate of 0.1C to 2.8V, stand it for 3 minutes, and then Charge at a rate of 0.1C to 4.2V, so one charge and one discharge is counted as one cycle; according to the above rules, the rate test is completed at 0.2C, 0.5C, and 1.0C for 5 cycles respectively, and finally at 0.2C Charge to 4.2V at a rate of 4.2V, stand still for 3min, discharge at a rate of 0.5C to 2.8V, stand still for 3min, and cycle up to 50 times.

The electrochemical performance of the lithium battery was obtained as follows:

0.1C, 0.2C, 0.5C, 1.0C lithium ion battery specific capacity.

100 cycle retention rate = specific capacity of the first charge / specific capacity of the 100th cycle × 100%;

200 cycle retention rate = specific capacity of the first charge / specific capacity of the 200th cycle × 100%;

Retention rate of N hundredth cycle = charging specific capacity for the first time / charging specific capacity for N hundredth cycle × 100%.

Preparation Example 1

1. Wetting of inorganic particles

Immerse 7.5g of ion-conducting particles (nano-silicon oxide) and 0.75g of conductive inorganic particles (acetylene black) into 10g of N-methylpyrrolidone (NMP), stir for 30min and then let stand for 24h.

2. Dissolution of polymers with functional groups on the side chain

Add 10.0 g of polyvinyl alcohol to 50 g of N-methylpyrrolidone, dissolve it at 65°C, and then cool down to 25°C.

3. Preparation of adhesive

The mixture prepared in step 1 and step 2 is dispersed at a high speed at 3000rpm, and 50gNMP is added to adjust the viscosity to 50000mPas. Adhesive A (polymer of functional groups on side chains: sum of mass of ion-conducting particles and conductive inorganic particles = 10: 8.25) was obtained.

Preparation example 2

Similar to Preparation Example 1, the amount of ion-conducting particles (nano-silicon oxide) in Preparation Example 1 was reduced to 5.0 g, and the amount of conductive inorganic particles (acetylene black) was reduced to 0.5 g. Add 50g NMP to adjust the viscosity to 50000mPa·s. Adhesive B (polymer of functional groups on side chains: sum of mass of ion-conducting particles and conductive inorganic particles = 10: 5.5) was obtained.

Preparation example 3

Similar to Preparation Example 1, the amount of ion-conducting particles (nano-silicon oxide) in Preparation Example 1 was reduced to 2.5 g, and the amount of conductive inorganic particles (acetylene black) was reduced to 0.25 g. Add 50g*× to adjust the viscosity to 50000mPa·s. Adhesive C (polymer of functional groups on side chains: sum of mass of ion-conducting particles and conductive inorganic particles = 10: 2.75) was obtained.

Preparation Example 4

Similar to the steps of Preparation Example 1, the difference is that NMP is replaced by water as a solvent to obtain adhesive D (the quality of the polymer containing functional groups on the side chain: the sum of the mass of ion-conducting particles and conductive inorganic particles=10:8.25 ). The viscosity of the adhesive is 60000mPa·s.

Preparation Example 5

Similar to the steps of Preparation Example 2, the difference is that the ion-conducting particles (nano-silicon oxide) are replaced by nano-alumina to obtain adhesive E (polymer quality containing functional groups on the side chain: ion-conducting particles and conductive inorganic particles Sum of masses = 10:8.25). The viscosity of the adhesive is 60000mPa·s.

Embodiment 1 Adhesive A prepares lithium-ion button battery (NMC622 electrode)

1) Preparation of electrode slurry: 3.8072g NMC 622, 0.7065g adhesive A

, 0.1071g conductive carbon black (Super-P) mixed with 2.6g NMP, ball milled for 2 hours;

2) Coating: evenly coat the electrode slurry on the aluminum foil, and dry it under vacuum at 100°C for 12 hours;

3) Die-cutting of the pole piece: After the vacuum-dried pole piece is rolled, it is punched to obtain a circular electrode piece with a diameter of 16mm;

4) Preparation of button-type half-cells: After the circular electrode sheet was vacuum-dried at 80°C for 12 hours, it was transferred to a dry argon glove box and paired with metal lithium to form a button-type half-cell. The electrolyte was 1mol/L lithium hexafluorophosphate (solvent: Ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1 (V)); Add 3wt% functional additive tris(trimethylsilyl) in electrolyte ) Phosphate ester; the diaphragm is a polypropylene diaphragm.

And test the cycle and rate performance of the lithium ion battery prepared in Example 1 as shown in Table 1 and Figure 2.

Embodiment 2 Adhesive B prepares lithium-ion button battery (NMC622 electrode)

Similar to Example 1, the difference is that the composition B in Preparation Example 2 was used as the adhesive to prepare a lithium-ion button battery, and the cycle and rate performance of the lithium battery prepared in Example 2 were tested as shown in Table 1 and Figure 2.

Embodiment 3 Adhesive C prepares lithium-ion button battery (NMC622 electrode)

Similar to Example 1, the difference is that the composition C in Preparation Example 3 was used as the adhesive to prepare a lithium-ion button battery, and the cycle and rate performance of the lithium battery prepared in Example 3 were tested as shown in Table 1 and Figure 2.

Example 4 Adhesive D prepares lithium ion button battery (LFP electrode)

Similar to Example 1, the difference is that lithium iron phosphate (LFP) is used as the electrode material, water is used as the solvent, and the composition D in Preparation Example 4 is used as the adhesive to prepare a lithium-ion button battery, and the preparation of Example 4 is tested. The cycle and rate performance of the lithium battery are shown in Table 1 and Figure 3.

Embodiment 5 Adhesive D prepares lithium-ion button battery (silicon carbon electrode)

1) Preparation of electrode slurry: mix 1.6040 silicon carbon negative electrode, 1.3436 adhesive D and 0.2021g conductive agent, and ball mill for 2 hours;

2) Coating: evenly coat the electrode slurry on the copper foil, and vacuum process at 130°C for 12 hours;

3) Die-cutting of the pole piece: After the vacuum-dried pole piece is rolled, it is punched to obtain a circular electrode piece with a diameter of 16mm;

4) Preparation of button-type half-cells: After the circular electrode sheet was vacuum-dried at 80°C for 12 hours, it was transferred to a dry argon glove box and paired with metal lithium to form a button-type half-cell. The electrolyte was 1mol/L lithium hexafluorophosphate (solvent: Ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1 (V)); Add 3wt% functional additive-fluoroethylene carbonate ( FEC); the diaphragm is a polypropylene diaphragm.

And test the cycle performance of the lithium-ion battery prepared in Example 5 as shown in Figure 4.

Embodiment 6 Adhesive E prepares lithium-ion battery (silicon carbon electrode)

Similar to Example 5, the difference is that the composition E in Preparation Example 5 was used as an adhesive to prepare a lithium ion battery, and the cycle performance of the lithium battery prepared in Example 6 was tested as shown in Figure 4 . Comparative example 1 polyvinyl alcohol prepared lithium ion battery (NMC622 electrode)

Similar to Example 1, the difference is that polyvinyl alcohol is used as an adhesive, and the cycle and rate performance of the lithium battery prepared in Comparative Example 1 are tested, as shown in Table 1 and Figure 2.

Comparative Example 2 Polyvinyl Alcohol Preparation Lithium-ion Battery (LFP Electrode)

Similar to Example 4, the difference is that polyvinyl alcohol is used as the adhesive, and the cycle and rate performance of the lithium battery prepared in Comparative Example 2 are tested, as shown in Table 1 and Figure 3.

Comparative example 3 polyvinyl alcohol prepared lithium ion battery (silicon carbon electrode)

Similar to Example 5, the difference is that polyvinyl alcohol is used as the adhesive, and the cycle performance of the lithium battery prepared in Comparative Example 3 is tested as shown in Figure 4.

Table 1 Adhesive used in different cathode materials to prepare electrochemical performance table of lithium ion battery

Description of attached drawing 1:

It can be seen from the differential scanning calorimetry (DSC) spectrum (Figure 1) of the adhesive D that, unlike PVA, the adhesive-D (PVA+SiO ₂ ) of Preparation Example 4 has a larger Significant endothermic peaks appear in the temperature range. The reason may be the dehydration cross-linking reaction between the hydroxyl groups on the PVA side chain and the hydroxyl groups on the SiO ₂ surface.

Explanation of Table 1, Attached Figure 2, and Attached Figure 3:

From the ratio data of lithium particle batteries in Examples 1 to 4 and Comparative Examples 1 to 2, it can be seen that when pure PVA is used as the adhesive (Comparative Example 1 and Comparative Example 2), due to the poor conductivity and ion-conducting properties of PVA, its preparation The high-rate specific capacity of the electrode is significantly lower than that of the adhesive containing inorganic particles (Examples 1-4). With the increase of the total content of ionic particles and conductive inorganic particles in the adhesive, the rate performance of the button battery is significantly improved. The reason is that the interface of the ion-conducting particles has the function of transporting lithium ions. As the content of the ion-conducting particles increases ( Examples 1-3 use adhesives A, B and C respectively, in which the mass ratios of the sum of ion-conducting particles and conductive inorganic particles to the mass of the polymer are 8.25, 5.5 and 2.75), forming a more complete ion-conducting network. Lithium-ion batteries prepared with binders with higher content of ion-conducting particles exhibited better rate performance.

Figure 4 explains:

From the cycle data of the lithium-ion batteries of Examples 5, 6 and Comparative Example 3, it can be seen that through 100 cycles, the cycle retention rate of the silicon-carbon negative electrode in Example 5 is greater than 95%; after 500 cycles, the The lithium-ion battery prepared in and 6 still maintains a high specific capacity (about 400 mAh/g, which is higher than the theoretical specific capacity of graphite 372 mAh/g). It shows that the thermally crosslinked adhesive can effectively inhibit the volume expansion of silicon-based materials. At the same time, at the same magnification (0.2C), the specific capacity without ion-conducting particles (Comparative Example 3, 206mAh/g) is also smaller than that containing ion-conducting particles (Example 5, 734mAh/g). The interfacial ion transport function of ion-conducting particles is further proved.

The above are only a few embodiments of the application, and do not limit the application in any form. Although the application is disclosed as above with preferred embodiments, it is not intended to limit the application. Any skilled person familiar with this field, Without departing from the scope of the technical solution of the present application, any changes or modifications made using the technical content disclosed above are equivalent to equivalent implementation cases, and all belong to the scope of the technical solution.

Claims (10)

1. An adhesive is characterized in that the adhesive is prepared by mixing a mixture of a rubber and a resin,

the adhesive comprises a polymer with a side chain containing functional groups, inorganic particles and a solvent;

the mass ratio of the polymer containing the functional group on the side chain to the inorganic particles is 10: 2-2: 10;

the inorganic particles include conductive inorganic particles and ion conductive inorganic particles;

the mass ratio of the conductive inorganic particles to the ion-conductive inorganic particles is 10:1 to 1:10.

2. the adhesive of claim 1,

the functional group is selected from at least one of hydroxyl, carboxyl, amino, isocyanate group, epoxy group or ester group;

preferably, the polymer is selected from at least one of polyurethane, polyvinyl alcohol, polyacrylic acid, polyvinyl acetate, polyacrylamide, carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, or hydroxyethyl cellulose salt;

preferably, the conductive inorganic particles are selected from at least one of metal particles, graphite, acetylene black, or carbon nanotubes;

preferably, the metal particles are selected from at least one of Be, al, ti, V, fe, co, zn, ge, zr, ag, sn, au or Mn;

preferably, the ion-conducting inorganic particles are selected from at least one of metal oxides, non-metal oxides or metal fluorides;

preferably, the metal oxide is selected from at least one of oxides of Be, al, ti, V, fe, co, zn, ge, zr, ag, sn, au or Mn;

preferably, the non-metal oxide is selected from silica;

preferably, the metal fluoride is selected from at least one of fluorides of Be, al, ti, V, fe, co, zn, ge, zr, ag, sn, au or Mn.

3. The adhesive of claim 1,

the adhesive also contains a wetting agent;

preferably, the wetting agent is selected from at least one of alkyl sulfate, sulfonate, fatty acid ester sulfate, carboxylic acid soap, phosphate ester, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer or silanol nonionic surfactant;

preferably, the content of the wetting agent is 0 to 5.0wt% of the adhesive;

preferably, the adhesive also contains a thickening agent;

preferably, the thickener is selected from a low molecular thickener and/or a high molecular thickener;

preferably, the low molecular weight thickener is at least one selected from inorganic salt thickeners, fatty alcohol thickeners, fatty acid thickeners, alkanolamide thickeners, ether thickeners, ester thickeners or amine oxide thickeners;

preferably, the polymer thickener is at least one selected from cellulose thickeners, polyacrylic acid thickeners, polyurethane thickeners, natural gum thickeners and polyoxyethylene thickeners;

the content of the thickening agent is 0-5.0 wt% of the adhesive.

4. A method for preparing the adhesive according to any one of claims 1 to 3,

at least comprises the following steps:

mixing raw materials containing a polymer, conductive inorganic particles, ion-conducting inorganic particles and a solvent to obtain the adhesive.

5. The production method according to claim 4,

the mixing comprises the following steps:

dissolving conductive inorganic particles and ion-conductive inorganic particles in a solvent to obtain a mixture I;

dissolving a polymer in a solvent to obtain a mixture II;

mixing the mixture I and the mixture II;

the mixing temperature is 25-100 ℃.

6. The production method according to claim 4,

the solvent is at least one of water, N-methyl pyrrolidone, dimethylformamide, tetrahydrofuran, acetone, butanone, ethanol, isopropanol or acetonitrile;

the mass of the solvent is as follows: the sum of the masses of the polymer, the conductive inorganic particles and the ion-conductive inorganic particles is from 1 to 1:1;

optionally, the raw materials also contain a wetting agent;

optionally, the raw material further comprises a thickening agent.

7. An electrode material for a lithium ion battery, characterized in that,

the electrode material for the lithium ion battery comprises a positive electrode material and a negative electrode material;

the positive electrode material is selected from LiCoO ₂ 、LiNiO ₂ 、LiMnO ₂ 、LiMn ₂ O ₄ 、LiMn _x Ni _y Co _1-x-y O ₂ 、LiVO ₂ 、Li _x V ₂ O ₄ 、Li _x V ₃ O ₈ 、LiFeO ₂ Or LiFePO ₄ At least one of;

wherein, x ranges from 0.1 to 2; y ranges from 0.1 to 2;

the negative electrode material is selected from at least one of artificial graphite, natural graphite, activated carbon, a silicon-based negative electrode material or a tin-based negative electrode material;

the positive electrode material and/or the negative electrode material contains the adhesive according to any one of claims 1 to 3 or the adhesive obtained by the production method according to any one of claims 4 to 6;

preferably, the adhesive needs to be subjected to heat crosslinking treatment when in use;

preferably, the temperature of the thermal crosslinking is 80-200 ℃;

preferably, the temperature of the thermal crosslinking is 100 ℃ to 150 ℃.

8. A preparation method of a lithium ion battery electrode is characterized in that,

at least comprises the following steps:

mixing materials containing electrode materials and conductive agents, and performing ball milling to obtain slurry;

coating the slurry on the surface of a substrate, and drying to obtain the lithium ion battery electrode;

wherein, when preparing the positive electrode, the electrode material is selected from the positive electrode material in claim 7;

when preparing a negative electrode, the electrode material is selected from the negative electrode materials described in claim 7.

9. The method of claim 8,

the conductive agent is selected from conductive carbon black, carbon nano tubes or graphene;

the dosage ratio of the electrode material to the conductive agent is 65-99;

preferably, the ball milling time is 1-5 h;

preferably, the drying temperature is 80-200 ℃;

preferably, the drying time is 4-24 h;

preferably, the drying is performed under vacuum conditions;

preferably, the vacuum degree of the drying is-0.02 to-0.1 MPa.

10. A lithium ion battery is characterized in that,

the lithium ion battery employs the positive electrode and/or the negative electrode prepared according to claim 9.

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